The present invention relates in general to directional couplers and is concerned, more particularly, with a technique for constructing a more compact four port, two branch directional coupler by providing capacitive matching networks preferably at each port of the directional coupler.
FIG. 1 shows a prior art coupler network in stripline construction and substantially the same as the one referred to in my copending application Ser. No. 766,431. With the conventional coupler the physical line lengths 1 inversely relate to the operating frequency of the device. At the higher microwave frequencies there is no problem in that the line lengths are relatively short and the device can be made quite compactly. However, at the lower microwave frequencies the proportionately larger line lengths make the overall device quite large especially in comparison with the devices used at the higher frequencies.
Accordingly, an object of the present invention is to provide a directional coupler using distributed elements that can be constructed more compactly than prior art couplers and especially so when constructed for operation at lower microwave frequencies or UHF frequencies.
A further object of the present invention is to provide a compact branch coupler that is preferably constructed in stripline, and that can be fabricated quite easily in a compact form.